Kate Williams, librarian at the University of Oxford. Photograph: Felix Clay

Kate Williams always wanted to be a librarian. The trouble was she didn't know it. She studied English and Latin at Cambridge University, where she took pleasure in tracking down interesting material in the university's libraries. During one summer she took an internship at a law firm, and there she enjoyed using the archives to track down precedents and ancient cases. Then after graduating she taught English as a foreign language. "But again," she says, "I used to really enjoy taking my students into the library and using all the resources there, encouraging them to become independent learners." Her hands fidget gently in the chair of her tiny office. The shelves behind her are filled with files, and there are cardboard boxes on the floor.

Only when Williams's aunt decided to have a tactful word - exasperated, one imagines, by her niece's obtuseness - did the penny finally drop. "She said, 'Are you sure you want to be a teacher?'" Williams remembers. "And I said, 'I think so.' Then she said, 'Well how about being a librarian?' ... Then I looked back and thought, 'Oh yes, I have really enjoyed that aspect of helping people in the library.' And then it started to make sense." She does not actually slap her own forehead, but the idea seems to cross her mind.

Within a year, Williams had enrolled on Oxford University's graduate trainee scheme, after which she began her diploma to qualify as a librarian. (It is a proper profession, you know, like law or accounting.) And since then she has risen fast to become the university's subject librarian with responsibility for the education library - a resource for people doing teacher-training courses or conducting research into any aspect of education, a subject that is still close to Williams's heart. Does her aunt, nevertheless, take all the credit for her career these days? "I think she's very pleased," she says with a smile. "If she could go back again, she says she would definitely want to have been a librarian."

Though her choice of profession may look obvious now, Williams can surely be forgiven for her years of prevarication. After all, librarians, by reputation, are meant to be easy to forget about. They are said to be people who only assert their existence on the rest of us, if they really must, with an occasional fine or explosive shush. "I suppose it isn't really one of those career paths that people set out thinking they want to do," Williams shrugs. "I don't know whether children dream of being librarians in the way they do of being astronauts and artists." She clearly does know, but I try not to agree too wholeheartedly.

And yet this supposedly dusty old profession really has changed out of all recognition in the 29 years that Williams has been alive. Indeed "information management", as the field is also known, has become increasingly important - much more important, in all likelihood, than you thought. And the reason, of course, is technology.

Information is now very easy to find on the internet; however, more recondite material risks getting lost beneath the rising tide. "The amount of information out there is vast and constantly increasing," Williams explains, "and the ways of getting hold of it are constantly developing. There's a danger that people think it's getting easier to find information because you've got the major search engines. But they certainly don't help in an academic environment ... I spend quite a lot of my time trying to evaluate what people can do on a particular search engine, which is nice and easy to use, and what they can't."

Even so, I have to ask, does any truth remain in the old librarian stereotype? "I assume we're thinking of somebody fairly elderly with a bun, and quite fierce? That kind of stereotype?" Actually, I was thinking of the other one - the mild-mannered, mousey librarian stereotype - but either would do. Williams considers the question. "I think probably the truth of what a librarian is like has changed as much as the world that librarians are working in now," she says. "Because it isn't the case any more that you are shut away in a dusty room surrounded by books."

Although there does still seem to be a bit of that. A quick jaunt around the education library reveals that books have certainly not disappeared from her life. Thousands of them line every wall, covering every imaginable subject in the study of education. And in the past 18 months Williams has overseen the complete reclassification and rearrangement of them all - including the pesky oversized books that need specially large shelves, and the rarely used ones, which are kept in the basement in a line of huge, rolling stacks.

Nevertheless, it is true that the management of digitally held and online information is what occupies most modern librarians these days. And it is going to keep occupying them for some time. "So I don't know what kind of stereotype I fall under," says Williams, "but I would think that most people working now in Oxford libraries at the kind of level I'm at ... are often quite young, generally quite dynamic and quite forward-thinking, hopefully."

And there are plenty of important problems for such people to solve. Consider this issue, for instance, which Williams addressed in her dissertation when she was still qualifying as a librarian: How can junior doctors start treating patients in an incredibly busy environment and still keep up-to-date with all the changing clinical evidence that they need to make their decisions? "There is the danger," Williams explains, "that it can't really happen. And then people are relying on outdated information, or just something that they've asked a senior colleague about, and that person might have got their information years before. So how to keep it current is quite a challenge." To meet it, good librarians will be needed.

Although Williams is already quite busy enough with her own duties. Besides managing the education library, she teaches information skills to students and academics to help them find what they need more easily, while at the same time working towards a Fellowship of the Higher Education Academy. And then of course there is the enquiries desk in her own library, which must be staffed at all times, where Williams still works for about 10 hours a week during busy periods.

Despite the pressures on her time, however, this traditional face-to-face work is still something she particularly enjoys. "It's that idea of librarianship being like a detective role," she explains, her eyes lighting up. "People come to you wanting to find information, and you are able - hopefully - to help them track it down in places, perhaps, that they wouldn't know to look. Or in ways that they wouldn't know how to look."

One slight regret I sense from her, however, is that there is so little understanding out there of what librarians do - or how useful they are. "I think most people think it's probably quite a nice job," she says. "I think they imagine you sit in a room full of really nice interesting books and you get to read them, and help the odd person. I don't think they realise quite how busy it gets, or how much pressure you feel under."

So what kind of person does she think would be well suited to what life as a librarian is really like? "I guess some of the skills and personality types you need would probably be the same as it's ever been," she says. "You probably need to be fairly organised and methodical. You need to understand how to arrange and present information clearly." And is she like that? Does she keep her books carefully ordered at home?

To my surprise, Williams goes rather quiet for a moment. "How I deal with my books at home and how I deal with them at work is completely different," she explains diplomatically. "My partner also works in libraries, so we have a lot of books. Too many at the moment for the shelving in our flat ... I tend to be able to remember where I've put things, so I'll group things maybe by topic, but very roughly, in a way that probably only makes sense to me." She looks around a little warily, and then adds a note of caution: "It wouldn't be recommended," she admits, "if you wanted other people to use the collection."

Curriculum vitae

Pay "The salary scale for my job, which I'm about halfway through, is from about £28,000 to £35,000."

Hours "I aim to work 40 hours a week, 8am to 5.15pm, Monday to Friday. I do find myself working over that, but that's probably just me trying to be a perfectionist."

Work-life balance "I'd say it's fine. If it ever becomes less good it's just because I've said yes to too many things. My boss does say to me occasionally, 'Think about this 40-hour week. How's that going to work?'"

Best thing "Being part of the university, and part of an academic department. You feel like the library is incredibly valued."